1. Field of the Art
The invention relates generally to a method and apparatus for mounting an ejector to a die board and more particularly, to a glueless method and apparatus for mounting an ejector to a die board. The present invention also relates to an ejector configuration and more specifically to an ejector configuration for a rotary die.
2. Description of the Prior Art
The processing of sheet material such as corrugated board and the like to form a box, display device or the like, normally involves utilizing a rotary or flat cutting die. Various cutting and creasing rules are mounted to the cutting die to cut a blank of sheet material and provide it with various cuts, slits, scores and perforated lines for the purpose of forming tear-out areas, punched out areas, profiles, fold lines, etc. in the blank.
A rotary cutting press is constructed of two parallel mounted cylinders, namely, a die roll and an anvil roll which rotate counter to each other. One cylinder known as the cutting cylinder or die roll includes a die board and serves the purpose of driving a cutting die toward the other cylinder which is commonly known as the anvil cylinder. The anvil cylinder may be constructed of steel, or steel that is covered with a resilient material such as urethane. The cutting cylinder drives the cutting or creasing rule against the anvil surface to thereby cut, score, slit, etc. the sheet material introduced into the nip area between the rolls. A plurality of scrap ejectors are connected with the die board and associated with the cutting rules for ejecting the paperboard or corrugated stock away from the cutting and scoring rules as the sheet material passes through the nip between the rules. These scrap ejectors can take a variety of forms such as those shown in U.S. Pat. No. 5,111,725 issued to Simpson, U.S. Pat. No. 4,224,851 issued to Imai, and U.S. Pat. No. 3,946,627 issued to Hofmann. A common form of scrap ejector, however, is to use a piece of rubber or rubber-type material of various heights, shapes and densities adjacent or near the cutting rule to perform this scrap ejecting function. In general, the rubber material is secured to the surface of the die board in the scrap areas and are generally higher than the product ejection pieces. As the sheet material is fed through the nip between the rolls, the rubber material is compressed and the sheet material is cut or scored. Then, as the sheet material leaves the nip area, the rubber material expands, thereby ejecting the scrap away from the cutting rule or urging the sheet material away from the creasing rule.
The current method of mounting these rubber ejectors to a cutting die is to glue the various rubber blocks to the die board using several different methods. One of the most common methods is to use a contact adhesive that is brushed onto the outer surface of the die board in the areas where the rubber is to be mounted and onto the rubber pieces that will be mounted to the die board. A disadvantage of using contact adhesives is that the glue must be allowed to dry until it becomes tacky enough to form an instant bond between the die board and the rubber. Failure to do so will result in an incomplete bond around the outer edges of the rubber pieces, thereby allowing dust to build up in the gaps and eventually push the rubber piece loose from the die board. Although thinning agents can be added to the contact adhesive to reduce the drying time, this often adversely affects the bond. Further, replacement of rubber that has been glued to the die board with contact adhesive is quite labor intensive and often requires removing the rubber by chiseling it loose from the die board.
Another method is to mount the rubber to a rotary die using super glue because it sets fast and forms a strong bond. However, because most die boards are constructed of wood which is porous, the wood can soak up the glue before the rubber piece has had time to bond to the die board. Further, the uneven surface and voids that are sometimes present on wood can result in an incomplete bond. Although various means can be used to limit the rate at which the super glue is absorbed into the wood such as first sealing the wood or using a primer to reduce the set time of the glue, these all require extra time. Further, super glue is less flexible than other glues and does not allow the rubber to flex in the area of the bond between the die board and the rubber.
Pressure sensitive adhesives have also been used to secure the rubber to the die board. One type is a thin film, double sided adhesive which is applied to the rubber in sheet form. Another is applied to the rubber in liquid form. Both are intended to be used by applying the rubber with the pressure sensitive adhesive thereon directly to the board without the use of additional glues. However, pressure sensitive adhesives are sensitive to heat and directional forces. Accordingly, heat generated during a press run will often soften the adhesive to the point where directional forces of the die may cause the rubber to slide out of its desired location.
All three of the above glueing methods require special training, materials and tools both when the ejectors are applied to the die board initially as well as when repairs must be made. Because these repairs are frequently done when an ejector has failed during a production run and without removing the die board from the rotary press, the repairs must be made as quickly as possible to limit the amount of machine downtime. At the same time, if the repairs are done too quickly, so that they are done incorrectly, the die will not perform well and will limit the potential efficiency of the press.
Further, although the rubber scrap ejecting elements can be of various types, heights, shapes and densities, they are commonly rectangular blocks or strips that are glued to a surface of the die board or a recess therein. Most rubber scrap ejectors extend outwardly from the surface of the die board in a direction generally perpendicular or normal to the outer surface of the die board. Thus, as the rubber ejector passes through the nip between the rollers, the rubber is compressed and then springs back to eject the scrap material. Various other xe2x80x9ccantileverxe2x80x9d type scrap ejectors also exist. Examples include those illustrated in U.S. Pat. Nos. 5,111,725, 4,224,851 and 3,946,627. A scrap ejector constructed exclusively of a rubber-type material also exists in the form of a generally V-shaped ejector with one leg of the V glued to the die board and the other leg of the V extending in cantilever fashion outwardly at an angle from the die board. In this ejector, the cantilever portion of the scrap ejector is compressible about the junction point of the V and functions to exert an outward force against the scrap material after passing through the nip between the rollers. Despite these prior designs, however, a need continues to exist for improved and longer lasting scrap ejectors.
Accordingly, there is a need it the art for an improved ejector configuration and design such as a scrap or product ejector or the like which is constructed solely of rubber or a rubber-like material and also an improved method and apparatus for mounting rubber or rubber-type ejectors to a die board without the use of glue.
In contrast to the prior art, the present invention provides a unique ejector and a unique mounting concept by which the ejector, and in particular an ejector constructed exclusively of a rubber material, can be mounted to a die board of a cutting die without the use of glue. Although, the main use of the ejector of the present invention is as a scrap ejector, the concepts and structure of the invention may also be used for product ejection, for sheet control or for other purposes. Thus, unless otherwise qualified, the term ejector or scrap ejector shall mean an ejector for product ejection, sheet control and other purposes.
More specifically, the mounting apparatus is comprised of a die board having an outer surface and an inner surface and an ejector retaining recess within the die board. The ejector retaining recess includes an opening in the outer surface of the die board and a recess shoulder portion positioned between the outer and inner surfaces of the die board.
The ejector to be mounted in this retaining recess is preferably constructed exclusively of rubber or a rubber-like material which is flexible and compressible. This ejector element generally includes a mounting end for mounting to the retaining recess in the die board, an opposite free end and an intermediate or ejector portion positioned between the mounting end and the free end. The mounting end preferably includes a neck portion and a pair of protruding shoulder portions extending outwardly from the walls of the neck. Preferably, the size and cross-sectional configuration of the ejector neck approximates the size and cross-sectional configuration of neck portion in the die board recess and the size and configuration of the protruding shoulder portions approximates the size and configuration of the retaining shoulder portions of the die board. Accordingly, when the mounting end of the ejector element is inserted into the retaining recess, engagement between the corresponding neck portions and the protruding and retaining shoulder portions secures the ejector element to the die board.
The ejector element in accordance with the present invention can be constructed of a variety of materials; however, it is contemplated that the ejector element will be constructed of a single rubber or rubber-like material throughout its entirety. The specific rubber-type material may vary depending upon specific uses and its expected life span. For example, a more costly and durable elastomer may be selected for use on high volume dies, while a lower cost and less durable rubber or elastomer may be used on low volume dies. The preferred embodiment is a closed cell and highly durable synthetic polyurethane elastomer material sometimes referred to as xe2x80x9cvulcell elastomerxe2x80x9d. In general, any material, whether natural or synthetic, which is compressible or resilient and compressible can function as the ejector material in accordance with the present invention
Accordingly, it is an object of the present invention to provide an improved mounting system for an ejector such as a scrap ejector.
Another object of the present Invention is to provide a cutting die with an improved ejector mounting system.
A further object of the present invention is to provide a glueless ejector mounting system for a die board.
Another object of the present invention is to provide an improved ejector structure.
A still further object of the present invention is to provide a method of mounting a rubber or rubber-like ejector to a die board.